Seasonal Effects on Leachate Quality from an Ozark Highlands Managed Grassland Using Automated, Equilibrium‐Tension Lysimeters

Core Ideas Lysimeters aid subsurface water quality assessments in long‐term nutrient management plots. Broiler litter rates affected few leachate quality parameters during a continuous 8‐yr period. Leachate water quality was affected by season during a continuous 8‐yr period. In regions with concentrated broiler (Gallus gallus) production, land application is a useful means of managing broiler litter (BL). However, surface and subsurface water quality issues may arise when continued annual BL application to fields occurs for extended periods. The application of manure follows seasonal guidelines for surface water quality protection. The objective of this study was to evaluate the effects of BL rate (0, 5.6, and 11.2 Mg litter ha−1) and season on drainage and leachate water quality over an 8‐yr period (2003–2011) in the Ozark Highlands with karst geology using automated, equilibrium‐tension lysimeters. During the 8‐yr period, seasonal drainage was unaffected by season or BL rate, averaging 118 mm per season. Averaged across BL rates, seasonal leachate pH, electrical conductivity (EC), flow‐weighted mean (FWM) NO3–N, dissolved organic C, S, and Zn concentrations, and NH4–N, Cu, Fe, and Se loads differed (P < 0.05) among seasons. Averaged across seasons, seasonal leachate EC, FWM PO4–P, total P, and S concentrations, and Ni load differed (P < 0.05) among BL rates. With the exception of As and Se, seasonal FWM leachate Cd, Cr, Cu, and NO3–N concentrations were at least five times smaller than their maximum contaminant level for drinking water during any of the four seasons. Since rainfall patterns seasonally change in many regions of concentrated poultry production, seasonal differences in the leachate water quality response to continuous annual application of BL are important to help tailor best management practices to protect soil and water resources in regions underlain by karst geology.